The present disclosure relates to an image forming apparatus to be connected to a three-phase four-wire alternating current power supply, and a method of controlling the image forming apparatus.
When a building is newly constructed or renovated, indoor wiring works are performed. For example, when the wiring work of a single-phase three-wire system is performed, an L conductor, a neutral conductor, and a grounding conductor are connected to a wall outlet arranged in each room. However, there is a case in which erroneous wiring is performed during the wiring work (inappropriate conductors are connected to a terminal of a wall outlet).
The following exemplary tester is known that is configured to determine whether or not the wiring is erroneous. Specifically, a wiring check tester is known that involves, with respect to a wall outlet including a first terminal to which an L (line) conductor configured to supply a single-phase alternating current voltage at a first frequency is connected, a second terminal to which an N (neutral) conductor is to be connected, and a third terminal to which an E (earth) conductor is to be connected, passing a current including a second frequency different from the first frequency between the second terminal and the third terminal, measuring a voltage signal between the first terminal and the second terminal, measuring a voltage signal between the first terminal and the third terminal, and detecting a magnitude relationship between frequency components corresponding to the second frequency included in the respective measured voltage signals, to thereby determine whether or not the N conductor and the E conductor are erroneously wired.
In a three-phase four-wire alternating current power supply, a load is connected between an L conductor (voltage line, active line) routed from one end of a Y connecting wire (on secondary side of a transformer) and a neutral conductor connected to a neutral point of the Y connecting wire. A current that flows out of the L conductor returns via the neutral conductor. The three-phase four-wire electric power distribution is employed in various countries around the world, including the USA, China, and India.
There is a problem in that, even when an image forming apparatus is connected to a correctly wired wall outlet, erroneous wiring in some other wall outlet in the building may affect the image forming apparatus to cause a failure. This problem is described with reference to FIG. 7. FIG. 7 is an explanatory view for illustrating a failure that may occur in the image forming apparatus due to erroneous wiring.
Referring to FIG. 7, in a wall outlet to which an electrical appliance 700 is connected, a neutral conductor is connected to a terminal (receptacle) for a grounding conductor, and a grounding conductor is connected to a terminal (receptacle) for a neutral conductor. Thus, the wiring is incorrect. In other words, the electrical appliance 700 is connected to a wall outlet in which the grounding conductor and the neutral conductor are miswired. As illustrated in FIG. 7, the electrical appliance 700 is an apparatus that operates with electricity, such as an air conditioner (not necessarily an air conditioner). In the example illustrated in FIG. 7, the neutral conductor of the wall outlet for the electrical appliance 700 is connected to a grounding conductor of a wall outlet for an image forming apparatus 800. Further, referring to FIG. 7, the image forming apparatus 800 and a PC 900 are connected to correctly wired wall outlets (wall outlets without miswiring), respectively.
The image forming apparatus 800 is, for example, a multifunction peripheral or a printer. Further, as illustrated in FIG. 7, there is a case in which, for the purpose of sending print data from the PC 900 to the image forming apparatus 800, the image forming apparatus 800 and the PC 900 are communicably (electrically) connected to each other via a cable. It is often the case that an interface in accordance with the USB standard is used for the connection between the image forming apparatus 800 and the PC 900.
The electrical appliance 700 connected to the miswired wall outlet as illustrated in FIG. 7 passes, through the grounding conductor, an alternating current to be flowed through the neutral conductor. When the electrical appliance 700 passes the alternating current through the grounding conductor, the alternating current potential of the grounding conductor fluctuates. Such fluctuation causes a frame ground potential difference between appliances (in the example illustrated in FIG. 7, the image forming apparatus 800 and the PC 900) connected to wall outlets arranged in the same building. Further, although depending on structures of buildings, a grounding conductor generally has a higher impedance than a neutral conductor, and hence the frame ground potential difference may be too large to be disregarded.
As illustrated in FIG. 7, the image forming apparatus 800 and the PC 900 are connected via the cable. When a non-isolated interface circuit such as a USB is used for this connection, and there is a frame ground potential difference between the image forming apparatus 800 and the PC 900, an alternating current i0 flows through a ground line of the interface circuit or a ground line of the cable. Joule heat generated by the alternating current i0 increases the temperature of the interface circuit, with the result that a failure may occur in the interface circuit. The interface circuit is generally not designed to pass a large current therethrough. As described above, there is a problem in that, when a wall outlet, which includes the grounding conductor erroneously connected to the receptacle (terminal) for the neutral conductor and the neutral conductor erroneously connected to the receptacle (terminal) for the grounding conductor, is arranged in the building, a failure may occur in the interface circuit of the image forming apparatus due to an output current of an electrical appliance connected to the miswired wall outlet.
The related-art electric power distribution tester (voltage detector) described above can be used to determine whether or not the wiring in the wall outlet used for the connection is correct. However, the tester cannot determine whether or not any other miswired wall outlet is arranged in the building. Therefore, whether or not there is a miswired wall outlet that is not tested with the electric power distribution tester in the building cannot be determined, and thus, whether or not a failure of the interface circuit of the image forming apparatus occurs cannot be determined.